This invention relates to a separation device and in particular to a separation device suitable for use in subsea locations to permit the separation of stabplates once the retainer or retaining mechanism used to secure the stabplates to one another, in use. has been disengaged.
The use of equipment located at the sea bed is commonplace in the extraction of oil and gas from subsea wells, for example to control the pumping of hydrocarbon materials therefrom. Although the majority of the description herein relates to use in relation to the extraction of hydrocarbon materials, it will be appreciated that the invention is not restricted in this regard, and may be used in, for example, off-shore electrical generation and other subsea applications. Typically, a number of individual pieces of equipment are connected to a distribution unit via a series of flying leads. The distribution unit is connected to remotely located equipment, for example at the sea surface or on land, or at another suitable location, by an umbilical. The flying leads and umbilical are each, typically, of relatively complex form, for example comprising a number of electrical cables for the transmission of electrical power and/or control signals, fibre optical cables, hydraulic power/control lines and/or lines carrying chemicals for supply to the seabed located equipment. At each end of each flying lead and at the end of the umbilical there may be a connector, known as a stabplate, adapted to mate with a corresponding connector or stabplate provided on the equipment to which that lead is to be connected. As each lead is of complex form, it will be appreciated that the connectors are also of complex form so as to permit a plurality of lines of the lead, for example the electrical, hydraulic, fibre optic and/or chemical lines as mentioned hereinbefore, to be connected simultaneously to the corresponding parts of the connector of the equipment. The connectors used in such locations may be of the general type described and illustrated in copending British patent application publication number GB2467192 and corresponding applications filed overseas. A stabplate connector of this form includes a connector plate having a series of individual connectors provided thereon, each of which is adapted to connect to a corresponding connector of a second connector plate secured to the subsea equipment. A securing mechanism is provided to secure the connector plates to one another. As described in GB2467192, the securing mechanism may comprise an angularly movable shaft associated with one of the connector plates and having a non-circular end part adapted to be introduced into a similarly shaped socket of the other of the connector plates. In use, upon connection of the connector plates to one another, the end part of the shaft is introduced into the socket. It is then rotated through a suitable angle as to prevent retraction of the end part back out of the socket. The shaft is then placed under tension to securely clamp the connector plates to one another.
If there is a need to separate the connector plates, for example for maintenance to be undertaken, then the tensile load is removed from the shaft and the shaft returned to its original angular position so as to allow the connector plates to be separated. Separation of the connector plates, like connection thereof, is typically undertaken using an ROV, although in some circumstances a diver may undertake this work.
As the stabplates are generally installed and left in position for extended periods of time, marine deposits such as calcareous deposits, coral growth, etc, may result in the connector plates being retained to one another despite the release of the securing mechanism.
Furthermore, where chemical lines or hydraulic lines are provided, the valves incorporated into the connectors thereof may result in separation of the connector plates drawing a vacuum, and so a relatively large separating load may be required to force the connector plates apart against the drawing of such a vacuum.
To counter this and allow separation of the connector plates, release of the securing mechanism may also be adapted to apply a separating load to the connector plates to force them apart.
There may be circumstances in which the separating load applied by such a securing mechanism is insufficient or cannot be used to achieve separation. For example, the separating load may be insufficient to break apart the marine deposits. Furthermore, there may be circumstances in which a secondary release mechanism has had to be deployed to release the securing means, and such a mechanism may not incorporate means to apply a separating load. For example, some secondary release techniques involve decoupling the securing mechanism by shearing or the like, in which case it will not be possible to apply a separating load by way of the securing mechanism. Where separation of the connector plates is not possible in a simple and convenient manner, then the coupled connector, and associated pieces of equipment, may have to be moved to the surface for repair, which is a costly and time consuming operation.